Within physical process environments, durable items are essential elements in the various stages of the production process (each “durable item” is defined broadly as any process tool or other resource that is reused during physical processes, such as a furnace, for example). Such durable items are subject to normal wear and tear, as well as damage during use.
Conventional practice calls for re-qualifying such durable items either at specific time intervals based upon anticipated wear and tear (commonly referred to as “life expectancy”), or whenever a determination is made that a particular item is damaged.
By way of an example, photomasks (or reticles) are durable items that are used in lithography tools in semiconductor manufacturing facilities. Photomasks are subject to wear and tear, and re-qualification of the same is commonly initiated at pre-determined time intervals after a particular photomask is introduced into the physical process (i.e., at the end of the durable item's life expectancy; wherein a particular time interval is selected to ensure that the photomask remains viable for use in the process).
The re-qualification process of a photomask includes not only time spent reconditioning the item, but also time spent using the lithography tool for re-qualification of the mask rather than using the tool to manufacture products. Stated differently, conventional re-qualification practices result in the photomask being removed from the physical process at the expiration of some time interval, or life expectancy, and then it remains unavailable for use in the process for the entire lifetime of the re-qualification process.
In U.S. Pat. No. 4,351,029 (“the '029 Patent”), entitled “TOOL LIFE MONITORING AND TRACKING APPARATUS,” the invention is directed to monitoring the quality of a tool on a set of machine tools to obtain an optimum tool life (e.g., a maximum volume of metal removed by the tool before re-sharpening). As excessive tool wear and tear may lead to increased forces on the tool, causing tool failure and interruption of production, the '029 Patent relies on net power measurement and derives the integration thereof via a function of time to obtain by reference to experience with a similar tool, the life expectancy of a particular tool. The '029 Patent attempts to avoid critical events at the end of such life expectancy.
In U.S. Pat. No. 6,021,360 (“the '360 Patent”), entitled “PROCESS CONTROLLER FOR BALANCING USAGE OF TOOL SETS,” the invention is directed to monitoring usage of a tool on a set of machine tools and warns an operator, or prevents usage of a tool chosen by an operator, in order to balance usage among similar tools of a set of machine tools. The '360 Patent also teaches verifying operational conditions of tools of the set of machine tools through usage. In short, the operator is permitted full flexibility of tool choice unless tool usage becomes unbalanced, at which time the '360 Patent may limit usage based on length of consecutive usage and percentage of product processed by each tool.
In U.S. Pat. No. 6,427,090 (“the '090 Patent”), entitled “REQUALIFICATION CONTROLLER FOR DURABLES,” the invention is directed to controlling the time at which a durable item used in a manufacturing process is re-qualified. The '090 Patent emphasizes the time at which the durable item is re-qualified as a function of the occurrence of a predefined event.
In U.S. Pat. No. 6,429,783 (“the '783 Patent”), entitled “APPARATUS FOR INDICATING OPERATIONAL STATUS OF SEMICONDUCTOR FABRICATION EQUIPMENT,” the invention is directed to using status lights or other signs operable to indicate the operational status of a durable tool. The '783 Patent emphasizes use of the lights or signs to indicate that the tool is in use, available or in repair. The '783 Patent suggests use of a video camera system to monitor the status lights and to work with an automated system to generate a “warning” if the automated system and the status lights are in disagreement concerning the status of the durable tool.
While these exemplary inventions solve a variety of problems within the art concerning re-qualification of durable items, there is no systematic methodology to ensure proper re-qualification of durable items before the same are reintroduced into the production process, particularly as related to life expectancy, condition change with item usage pattern and item maintenance/re-qualification. There is simply no viable procedure for preventing operators from placing unqualified tools in the production process line. A need exists in the art for a method that encourages re-qualification of durable items, while maintaining a high-production volume of a high-quality product notwithstanding undetected unsuitable conditions or failure of a durable item within the physical process.